The Celts are a problem before they are a subject. No one writing about them in 2026 can pretend to be standing on solid ground, because the ground itself keeps shifting. The word Celt was a Greek catch-all before it was an ethnic name, a Roman administrative category before it was an archaeological one, and an eighteenth-century European fantasy before it was the name of a modern political movement. Barry Cunliffe, the Oxford archaeologist who has done more than anyone to write the Celts into the modern historical record, has spent a career gently reminding his readers that the Celts are whatever we decide to make of them.
What follows is a working sketch of that decision. It treats the Celts as the Iron Age peoples of Europe who shared a common material culture — initially the Hallstatt and then the La Tène art styles — and who spoke languages belonging to the Celtic branch of Indo-European. The language criterion is the load-bearing one, because it is the only one that allows us to follow the Celts through the historical record when their political reality has been lost. Everything else in this pillar follows from it.
The Hallstatt and La Tène Foundations
The deepest layer of Celtic civilization is the later Bronze Age, but the cultural explosion that gave the Celts their character took place in the early Iron Age. The first recognizable phase is the Hallstatt culture, named after the salt-mining site in the Salzkammergut region of Austria where the type-site cemetery was excavated in the nineteenth century. The Hallstatt phase is conventionally dated c. 800–450 BCE, with the spectacular princely burials — tumulus graves with rich Mediterranean imports — concentrated in the late Hallstatt D phase of c. 600–450 BCE.
The second phase is La Tène, which takes its name from the type site on the northern shore of Lake Neuchâtel in Switzerland, where thousands of objects were deposited in the lake (probably as votive offerings) between the third and first centuries BCE. La Tène art broke decisively with the geometric Bronze Age tradition and developed a fluid, plant-inspired, curvilinear visual vocabulary of tendrils, palmettes, lyre shapes, and abstract masks. Within a few generations of its development, La Tène style had spread from the Swiss plateau to Ireland, from the Po Valley to the middle Danube, and as far east as the Hungarian plains.
The equation of Hallstatt and La Tène with the spread of Celtic-speaking peoples is the standard textbook view, but it is not the only one. John T. Koch and the late John R. Collis, in the Celtic from the West papers and the 2010 volume of the same name, have argued that Celtic languages may have been spoken along the Atlantic façade of Europe from the late Bronze Age, and that the continental Iron Age may have spread Celtic culture as much as it spread Celtic languages. The traditional model and the revisionist one are not yet reconciled. The continental model, in which Celtic emerges in the Hallstatt heartland and radiates outward, remains the dominant view in most textbooks; the Atlantic model has the better evidence from place names and certain material-culture features. The question of where proto-Celtic was first spoken, and how it spread, is one of the most active areas of contemporary Celtic scholarship.
The Iron Age Expansion
Between roughly 500 and 200 BCE, the Celtic-speaking peoples of Europe underwent one of the most dramatic expansions of any pre-industrial civilization. The direction of greatest movement was westward, into Gaul and the British Isles, with the second being eastward, into the Balkans and ultimately into central Anatolia. The southern push, into the Po Valley and central Italy, brought the Celts into direct contact with Rome — most memorably in 390 (or 387) BCE, when a Senones war band under a chieftain whom the Romans called Brennus entered Rome itself, occupied most of the city, and was bought off with a substantial ransom. The story of the geese of the Capitol, whose cackling woke the garrison, has been a fixture of Roman patriotic legend ever since. The historical reality of the sack is supported by both Roman and Greek sources, and its psychological impact on the Roman imagination was enormous.
The expansion was not a single migration but a long, uneven process that touched different regions at different times and in different ways. By the late fourth century BCE the Celtic world had reached its widest extent, a vast arc of related peoples stretching from the Atlantic to the Black Sea. Major tribal groupings of the period — the Boii in Bohemia, the Volcae Tectosages in the middle Danube, the Helvetii in the Swiss plateau, the Arverni in central Gaul, the Senones in northern Italy and the Yonne valley — were among the most powerful political entities in the ancient world, and their leaders could raise armies of tens of thousands. Caesar counted more than sixty separate peoples in Gaul on the eve of the Roman conquest.
The continental Celtic heartland was rich in iron, copper, tin, gold, and salt. The salt mines at Hallstatt itself continued in production well into the La Tène period, and the trade in salt, iron, and bronze brought Celtic goods and Celtic merchants to every part of the European continent. La Tène art and the La Tène economic system were, in effect, the two halves of a single phenomenon: an industrial and artistic complex whose prestige was such that even non-Celtic-speaking elites across Europe wanted to be buried with La Tène objects.
Encounter with Rome
The Roman conquest of the Celtic world was not a single event but a long process. The Celts of the Po Valley, whom the Romans called the Galli Cisalpini, were defeated in the third and second centuries BCE and incorporated into the Roman state. The decisive phase was the conquest of Gaul between 58 and 51 BCE, documented in Caesar’s own De Bello Gallico. The campaigns against the Helvetii, the Belgae, the Veneti, the Arverni, and the great coalition led by Vercingetorix reduced the independent Celtic world of Gaul to a network of Roman provinces. The dramatic siege of Alesia in 52 BCE — in which Caesar surrounded the hilltop town with a circumvallation more than twenty kilometres long, then built a second wall facing outward when a relief force approached — trapped Vercingetorix and effectively ended independent Celtic political life on the continent. The chief himself was taken to Rome, displayed in Caesar’s triumph, and executed six years later.
Britain was invaded under Claudius in 43 CE and largely incorporated within a generation, although Wales, northern England, and most of Scotland remained unconquered for decades, and the Roman frontier at Hadrian’s Wall and later the Antonine Wall was a constant zone of military pressure. Ireland, lying west of the new province, was never conquered.
The Roman conquest was not the end of Celtic culture. Roman Gaul quickly developed a vibrant Gallo-Roman civilization that blended Celtic and classical elements. The great sanctuaries at the sources of the Seine (Sequana), the Marne (Matrona), the Moselle (Mosella), and the Saône (Arar) — to take only the most famous — continued to function as Celtic cult centres into the late empire. The Celtic languages of Gaul survived for centuries in rural and provincial areas, and the French rural place-name layer, the personal names preserved in Latin inscriptions, and a substantial number of Latin words of Celtic origin (including bracelet, char, manteau, and soc) all attest to a long Celtic substrate.
The Insular Celtic Exception
Ireland, never part of the Roman Empire, developed a distinctive and brilliant Celtic civilization throughout the early medieval period. The conversion of the island to Christianity in the fifth century, traditionally associated with the mission of Saint Patrick, produced a flowering of literacy, learning, and art whose legacy is preserved in a remarkable body of manuscripts, metalwork, and stone sculpture. Irish monks, working in a Christian intellectual tradition deeply informed by their native learning, established monasteries that became the intellectual centres of early medieval Europe. Columbanus (d. 615) and his followers carried the Irish monastic tradition to the continent, founding Bobbio in northern Italy, Luxeuil in eastern France, and a network of other houses that helped to re-Christianize much of Merovingian Europe.
The withdrawal of Roman military from Britain in the early fifth century CE, the arrival of the Angles, Saxons, and Jutes, and the long resistance of the Brythonic kingdoms of what is now Wales and the south-west produced a new political and linguistic map of the island. By the seventh century the Celtic-speaking regions of Britain had been pushed to the western and northern fringes: the kingdom of Strathclyde in the north, the kingdoms that became Wales in the west, the Cornish peninsula in the south-west, and the Pictish kingdoms of what is now Scotland. The so-called Celtic-speaking zone of the early medieval period was in many ways simply the continuation of a Celtic-speaking world that had never been fully Romanized in the first place.
The Viking age, beginning in the late eighth century, brought a new wave of upheaval. Norse raids devastated Irish monasteries and altered the political landscape of Scotland, the Hebrides, and the Isle of Man. Yet the Celtic-speaking communities persisted, and the resulting cultural mix produced the hybrid Norse-Gaelic culture of the Scottish Isles, the long Viking presence in Dublin, Waterford, and other Irish towns, and a remarkable body of literature produced in bilingual environments such as the Isle of Man.
The Medieval Celtic Societies
By the high middle ages, distinct Celtic-speaking societies had consolidated in Ireland, Scotland, Wales, Cornwall, Brittany, and the Isle of Man. Each developed its own legal traditions, literary conventions, and political structures, often under heavy pressure from larger neighbours. Wales was gradually absorbed by the English crown in the thirteenth through fifteenth centuries. Cornwall became effectively English-speaking, although the Cornish language lingered in remote areas into the eighteenth and early nineteenth centuries. Brittany maintained a distinct Celtic identity within the Kingdom of France, and the Breton language remained an important vernacular in the western part of the peninsula.
The Cornish case is the one that has been most rewritten by recent scholarship. Dolly Pentreath of Mousehole is still traditionally cited as the last native speaker of Cornish (died 1777), but the work of Kenneth George, Mark Kennedy, and others has complicated the picture, and the more cautious modern view is that Cornish survived in fragmentary form into the early nineteenth century. It has since been successfully revived as a community language. Manx, similarly, declined through the nineteenth and twentieth centuries and was declared extinct with the death of its last native speaker, Ned Maddrell, in 1974, before being revived in community use.
Ireland was the most distinctive of the medieval Celtic societies. The Brehon legal tradition, the clan-based politics of the tuatha, and an extraordinarily rich literary tradition that drew on both Christian and pre-Christian materials produced one of the great cultural records of medieval Europe. Scotland was politically complex, divided between a Gaelic-speaking Highlands, a Brythonic Celtic-speaking south (the old kingdom of Strathclyde), a Pictish north whose language is now lost, and an Anglo-Saxon-speaking lowland south-east. The gradual Gaelicization of much of Scotland produced a unified Gaelic cultural sphere that extended from the Highlands to the Hebrides.
The Decline of the Celtic Languages
From the high middle ages onward, the Celtic-speaking world was progressively marginalized. Political conquest, religious reform, economic pressure, and the cultural prestige of English and French worked together to reduce the geographic and demographic range of the Celtic languages. The Welsh case is the most robust. Welsh, supported by a long tradition of literary production, by the nonconformist chapels of the eighteenth and nineteenth centuries, and by official language policy in modern Wales, remains the most widely spoken of the Celtic languages, with several hundred thousand speakers. Irish, with official status in the Republic of Ireland, has had a more complicated history: a small but active traditional Gaeltacht community and a much larger population of second-language speakers. Scottish Gaelic retains a strong presence in the Western Isles despite centuries of decline. Breton is the only Celtic language spoken on the continent of Europe today, but it too has lost ground to French.
The Modern Invention of the Celts
The Celts as a subject of historical and cultural interest are, in substantial part, an invention of the modern period. The eighteenth-century antiquarian movement, the rediscovery of the Welsh and Irish manuscript traditions, the romanticization of Highland Scotland by James Macpherson and Sir Walter Scott, and the political movements of the nineteenth and twentieth centuries all contributed to the formation of a modern Celtic identity that has as much to do with the present as with the ancient world. The image of the noble Celt — long-haired, mystical, nature-loving, the last European to retain a sense of the spiritual unity of nature — is a Romantic construction with very little basis in the actual evidence. The nineteenth-century Eisteddfod, the Gorsedd of Bards invented by Iolo Morganwg, the Ossian poems that turned out to be almost entirely James Macpherson’s own work, the pseudo-ancient ceremonies of the Celtic Revival, and the modern Gaelic League, the Scottish National Mod, the Breton Gorsedd, and the Cornish Gorsedh Kernow are all, in their different ways, products of this construction.
Whether the modern Celtic identity is a continuation of ancient traditions or a romantic reinvention is a question that scholars continue to debate. There is no doubt, however, that the modern image of the Celts has had real political and cultural effects. It gave the Celtic-speaking peoples of the British Isles and Brittany a heroic past with which to identify, it distinguished them from their English and French neighbours, and it provided the foundation for the literary and artistic movements that became central elements of the cultural identity of Wales, Ireland, Scotland, and Brittany.
The next several pages dive more deeply into each period, each region, and each major aspect of this story. The origins and emergence of the Celts are explored through the Hallstatt and La Tène archaeological record. The Iron Age expansion is traced across the continent. The encounter with Rome is examined through the campaigns of Caesar, the Roman province of Gaul, and the long centuries of Roman Britain. The post-Roman Celtic survival is followed into the medieval period, and the Celtic presence in the British Isles is traced from the early medieval kingdoms to the present day.
Sources and Further Reading
Barry Cunliffe’s The Ancient Celts (Oxford UP, 1997) remains the most useful single-volume scholarly introduction, and his The Celts: A Very Short Introduction (Oxford UP, 2018) is a good shorter version. For the post-1997 update, see his Bretons and Britons: The Fight for Identity (Oxford UP, 2021). The standard treatment of the Iron Age Celtic economy is the late J. D. Hill’s The Pre-Roman Iron Age in Britain and Ireland (2001). For the revisionist view, the founding volume is John T. Koch and John R. Collis (eds.), Celtic from the West (Oxbow, 2010), and the wider case is built in Koch’s Tartessian (Oxbow, 2009) and his Outlern, Iberian (Oxbow, 2024). For the Roman campaigns, Caesar’s De Bello Gallico is the indispensable primary source, best read alongside the late J. F. Drinkwater’s Roman Gaul (Cornell UP, 1983). For early medieval Ireland, Dáibhí Ó Cróinín’s Early Medieval Ireland 400–1200 (Longman, 1995) is the standard scholarly synthesis, and the late Donnchadh Ó Corráin’s Ireland c. 800 (Cork UP, 2001) covers the Viking age and after. For the modern invention of the Celts, the late Peter Berresford Ellis’s Celtic Revivals (Faber, 2020) and the late Huw Pryce’s chapter in The Oxford Illustrated History of the Celts (OUP, 2018) are good introductions.